Spring 之 @Configuration 和 @Bean 注解

以你之姓@ 2023-06-16 02:00 7阅读 0赞

**目录**

关于Configuration

@Configuration+@Bean注册Bean

@Configuration+@Component注册Bean

@configuration中引入其它注解配置

@configuration嵌套静态Configuration类（须是静态类）

关于@Bean

@Bean定义生命周期的回调

@Bean的自定义命名

@Bean多个名字

@Bean定义描述信息

@Bean和@Scope的关系

--------------------

# **关于Configuration** #

@Configuration用于定义配置类，可替换xml配置文件，@Configuration就要提到他的好朋友@Bean，两个注解在一起可以创建简单的spring配置类，被注解的类内部包含一个或者多个被@Bean注解的方法，这些方法会被AnnotationConfigApplicationContext或AnnotationConfigWebApplicationContext类进行扫描，并用于构建bean定义，初始化Spring容器。

## **@Configuration+@Bean注册Bean** ##

原本的xml文件：

对等于@Configuration启动容器+@Bean注册Bean：

@Configuration 
    public class PeopleConfiguration { 
        @Bean 
        public People people() { 
            People people = new People();
            //注入
            people.setEyes(eyes()); 
            //注册bean
            return people; 
        } 
        @Bean  
        public Eyes eyes() { 
            return new Eyes(); 
        } 
    }

相关类：

public class People {
    
        public Eyes eyes;
    
        public void sayHello() {
            System.out.println("oh, hey man");
        }
        
        public void setEyes(Eyes eyes) {
            this.eyes = eyes;
        }
    
        public Eyes getEyes() {
            return eyes;
        }
        
        public void init() {
            System.out.print("初始化");
        }
    
        public void destroy() {
            System.out.print("销毁");
        }
    }

public class Eyes {
        public void test() {
            System.out.println("test");
        }
    }

测试Main类：

import org.springframework.context.ApplicationContext;
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    
    public class TestMain {
        public static void main(String[] args) {
            // @Configuration注解spring容器加载
            ApplicationContext context = new AnnotationConfigApplicationContext(PeopleConfiguration.class);
    
            //拿出bean
            People people = (People) context.getBean("people");
            people.sayHello();
    
        }
    }

![2019112317432550.png][]

## **@Configuration+@Component注册Bean** ##

和上面一样的例子，这次我们通过@Component申明注册Eyes

import org.springframework.stereotype.Component;
    
    @Component
    public class Eyes {
        public void test() {
            System.out.println("test");
        }
    }

Eyes注册到容器中我们在注入People类中的属性并且注册People

import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    
    @Component
    public class People {
        //注入
        @Autowired
        private Eyes eyes;
    
        public void sayHello() {
            System.out.println("oh, hey man");
        }
    
        public void setEyes(Eyes eyes) {
            this.eyes = eyes;
        }
    
        public Eyes getEyes() {
            return eyes;
        }
    
        public void init() {
            System.out.print("初始化");
        }
    
        public void destroy() {
            System.out.print("销毁");
        }
    }

配置类扫描包

import org.springframework.context.annotation.*;
    
    @Configuration
    //添加自动扫描注解，basePackages为People包路径
    @ComponentScan(basePackages = "com.xxx.xxx")
    public class PeopleConfiguration {
        PeopleConfiguration(){
            System.out.println("初始化");
        }
    }

main函数测试：

import org.springframework.context.ApplicationContext;
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    
    public class TestMain {
        public static void main(String[] args) {
            //@Configuration注解spring容器加载
            ApplicationContext context = new AnnotationConfigApplicationContext(PeopleConfiguration.class);
    
            //拿出bean
            People people = (People) context.getBean("people");
            System.out.println(people);
            people.sayHello();
    
        }
    }

结果：

![20191123174536709.png][]

## **@configuration中引入其它注解配置** ##

例：

import org.springframework.context.annotation.Configuration;
    import org.springframework.context.annotation.Import;
    import org.springframework.context.annotation.ImportResource;
    
    import com.xxx.xxx.MyConfiguration;
    
    @Configuration
    @ImportResource("classpath:applicationContext-configuration.xml")
    //导入配置类，可获取MyConfiguration中的Bean
    @Import(MyConfiguration.class)
    public class Config {
    }

## **@configuration嵌套静态Configuration类（须是静态类）** ##

例如：

import org.springframework.context.annotation.*;
    
    @Configuration
    //添加自动扫描注解，basePackages为TestBean包路径
    @ComponentScan(basePackages = "com.xxx.xxx")
    public class PeopleConfiguration {
        PeopleConfiguration(){
            
        }
        
        //嵌套(静态类)
        @Configuration
        static class TestConfig {
            @Bean
            Eyes eyes() {
                return new Eyes();
            }
        }
    }

--------------------

# **关于@Bean** #

上面介绍过了@Bean配合@Configuration可以代替xml的配置，方法中可以实现Bean之间的注入，如上方例子中的eyes注入到people中。

**@Bean的相关注意事项：**

1.  @Bean注解在返回实例的方法上，如果未通过@Bean指定bean的名称，则默认与标注的方法名相同； 
2.  @Bean注解默认作用域为单例singleton作用域，可通过@Scope(“prototype”)设置为原型作用域； 
3.  @Bean的作用是注册bean对象，那么也可以使用@Component、@Controller、@Service、@Ripository等注解注册bean，不过需要配置@ComponentScan注解进行自动扫描。

## **@Bean定义生命周期的回调** ##

@Bean支持两种属性，initMethod和destroyMethod，用于在实例化bean或者销毁bean的时候，调用指定的方法。

如上面的例子中的PeopleConfiguration类中的@Bean修改如下：

@Configuration
    public class PeopleConfiguration {
        @Bean(initMethod = "init", destroyMethod = "destroy")
        public People people() {
            People people = new People();
            //注入
            people.setEyes(eyes());
            //注册bean
            return people;
        }
        @Bean
        public Eyes eyes() {
            return new Eyes();
        }
    }

我们重新运行测试的Main方法效果如下：

![20191123174732323.png][]

在实例化people的时候调用了定义的initMethod

## **@Bean的自定义命名** ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5_size_16_color_FFFFFF_t_70][]

## **@Bean多个名字** ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5_size_16_color_FFFFFF_t_70 1][]

测试一下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5_size_16_color_FFFFFF_t_70 2][]

结果：

![20191123184618720.png][]

## **@Bean定义描述信息** ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5_size_16_color_FFFFFF_t_70 3][]

## **@Bean和@Scope的关系** ##

详细内容记录在我的这篇[https://blog.csdn.net/qq\_36652619/article/details/103214729][https_blog.csdn.net_qq_36652619_article_details_103214729]博客中

[2019112317432550.png]: https://img-blog.csdnimg.cn/2019112317432550.png
[20191123174536709.png]: https://img-blog.csdnimg.cn/20191123174536709.png
[20191123174732323.png]: https://img-blog.csdnimg.cn/20191123174732323.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20191123174746682.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20191123184545133.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20191123184602136.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5,size_16,color_FFFFFF,t_70
[20191123184618720.png]: https://img-blog.csdnimg.cn/20191123184618720.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20191123184643438.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjUyNjE5,size_16,color_FFFFFF,t_70
[https_blog.csdn.net_qq_36652619_article_details_103214729]: https://blog.csdn.net/qq_36652619/article/details/103214729